| A | B |
|---|
| AGL | Above Ground Level. Altitude expressed in feet measured above ground level. |
| ADF | Automatic Direction Finder. An aircraft radio navigation system which senses and indicates the direction to an L/MF non-directional radio beacon (NDB) ground transmitter. |
| Bearing | The horizontal direction to or from any point, usually measured clockwise from true north, magnetic north, or some other reference point through 360 degrees. |
| Dead Reckoning | Navigation of an airplane solely by means of computations based on airspeed, course, heading, wind direction and speed, groundspeed, and elapsed time. |
| DME | Distance Measuring Equipment. Equipment (airborne and ground) used to measure, in nautical miles, the slant range distance of an aircraft from the DME navigational aid. |
| FMS | Flight Management System. A computer system that uses a large database to allow routes to be preprogrammed and fed into the system by means of a data loader. |
| GA | All civil aviation operations other than scheduled air services and nonscheduled air transport operations for remuneration or hire. |
| GPS | Global Positioning System. A system which provides highly accurate position and velocity information and precise time, on a continuous global basis, to an unlimited number of properly equipped users. |
| IFR | Instrument Flight Rules. Rules governing the procedures for conducting instrument flight. |
| ILS | Instrument Landing System. A precision instrument approach system which normally consists of the following electronic components and visual aids: localizer, glideslope, outer marker, middle marker, and approach lights. |
| Indicated Airspeed | The speed shown on the aircraft airspeed indicator. |
| INS | Inertial Navigation System. An RNAV system which is a form of self-contained navigation. |
| Knots | Measure of the speed of aircraft and boats measured as nautical mile per hour or 6076 feet per hour. |
| LAAS | Local Area Augmentation System. Ground-based augmentation to GPS that focuses its service on the airport area (approximately 20-30 mile radius) for precision approach, departure procedures, and terminal area operations. |
| L/MF | Low or Medium Frequency. A frequency range between 190 and 535 kHz with the medium frequency above 300 kHz. |
| LORAN | Long Range Navigation. An electronic navigational system by which hyperbolic lines of position are determined by measuring the difference in the time of reception of synchronized pulse signals from two fixed transmitters. |
| Magnetic Course | Course of a vessel in relation to magnetic north. |
| Magnetic Deviation | Amount by which a ship’s magnetic compass needle points to one side or the other of magnetic north. |
| Magnetic Variation | A compass “error” resulting from the fact that at most points on the Earth’s surface the direction of the magnetic lines of force is not toward the geographic North Pole or South Pole. |
| MSL | Mean Sea Level. |
| NDB | Non-directional Beacon. An L/MF or UHF radio beacon transmitting non-directional signals whereby the pilot of an aircraft equipped with direction-finding equipment can determine their bearing to or from the radio beacon and "home" on or track to or from the station. |
| Pilotage | Navigation by visual reference to landmarks. |
| RNAV | Area Navigation (RNAV) provides enhanced navigational capability to the pilot. |
| Sextant | A sextant is a tool for measuring the angular altitude of a star above the horizon. |
| TACAN | Tactical Air Navigation. An ultra-high frequency electronic rho-theta air navigation aid which provides suitably equipped aircraft a continuous indication of bearing and distance to the TACAN station. |
| True Airspeed | The airspeed of an aircraft relative to undisturbed air. |
| True Course | A course corrected for variation and deviation that is referenced to geographic north. |
| True North | Geographical north. |
| UHF | Ultrahigh Frequency. The frequency band between 300 and 3,000 MHz. |
| VFR | Visual Flight Rules. Rules that govern the procedures for conducting flight under visual conditions. |
| VHF | Very High Frequency. The frequency band between 30 and 300 MHz. |
| VOR | Very High Frequency Omnidirectional Range Station. A ground-based electronic navigation aid transmitting very high frequency navigation signals, 360 degrees in azimuth, oriented from magnetic north. |
| VORTAC | A navigation aid providing VOR azimuth, TACAN azimuth, and TACAN distance measuring equipment (DME) at one site. |
| Vx | The speed at which the aircraft will produce the most gain in altitude in a given distance (best angle of climb). |
| Vy | The speed at which the aircraft will produce the most gain in altitude in the least amount of time (best rate of climb). |
| WAAS | Wide Area Augmentation System. Extremely accurate navigation system developed for civil aviation. |
| Waypoint | A predetermined geographical position. |
